1. Field of the Invention
This invention relates to an improvement in fine pitch connectors for connecting printed circuit boards (PCB) for board stacking, vertical to vertical, mother to daughter, vertical to right angle and/or straddle, and in one aspect relates to an improved connector comprising a plug and a socket each having four rows of electrical contact elements.
2. Description of the Prior Art
The art is replete with connectors for making multiple interconnections between boards, between boards and discreet wires, and between boards and flexible circuits, all of which have the goal of making the most interconnections per area of board space.
For example, board to board connectors are illustrated in WO 93/03513 published Feb. 18, 1993 and in U.S. Pat. No. 5,380,225 issued Jan. 10, 1995, available from the assignee of this patent (application). The publication illustrates a board to board interconnection of the hermaphroditic design wherein the connector portions have the identical shape and are mated in a single orientation to ensure proper electrical connection. Further, the solder tails of the connector portions are spaced 1 mm and each portion of the connector is formed to have a row of passive contacts (fixed contact surfaces) and a row of active contacts (movable spring contact surface). This relationship, according the publication, reduces the required overall PCB to PCB stack height (the distance between two coupled circuit boards) because only one spring height is required. Further, since each connector has both spring contacts and fixed contacts, the spring force on the movable contacts is the same from its initial mate height until the final mate height. The movable spring contacts are deflected by the same predetermined amount regardless of the PCB to PCB stack height. The latter patent referenced above teaches the use of a connector making four rows of contacts. This connector however discloses the contact elements of a passive nature in the plug 1a and the active, flexible contacts in the jack 1. The contact elements are however all spaced and staggered to form the four rows of contacts of equal number in one connector, lengthwise thereof. Other PCB to PCB interconnections are shown in WO 90/16093 where opposed spring contacts were employed which increased the stack height.
U.S. Pat. No. 4,804,336 discloses a D-shaped connector having improved density by using staggered rows of pin contacts in the body to double the density from the normal 50 contacts to 100. As in U.S. Pat. No. 5,380,225, staggering and duplicity alone does not serve to adequately improve the density of the interconnections to be made and still reduce the stack height.